Sicilian Defense

With 1...c5 Black fights for the d4-square without copying White's central pawn move. The usual follow-up is an exchange of the c-pawn for White's d-pawn, after which Black owns two central pawns against one and a half-open c-file that serves as the base for queenside counterplay. The price is time: the move develops no piece, and many lines add further pawn moves such as ...d6, ...e6, ...a6 and ...b5, so White often gains a lead in development and attacking prospects on the kingside.

The principal answer is 2. Nf3, which accounts for about half of all games in the Lichess database and prepares 3. d4 cxd4 4. Nxd4, the Open Sicilian. Black's main second moves are 2...d6, 2...Nc6 and 2...e6. After 2...d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 the Najdorf, 5...a6, is Black's most popular system, while 2...Nc6 3. d4 cxd4 4. Nxd4 e5 is the Löwenthal. Open lines are highly complex: White frequently castles queenside and advances on the other wing, and Black counters on the queenside and down the c-file. White can also decline to open the center with 3. Bb5, the Nyezhmetdinov-Rossolimo Attack after 2...Nc6.

Because Black is usually best prepared for the Open Sicilian, a range of anti-Sicilians is popular. 2. Nc3 keeps the d-pawn and leads to the Closed Sicilian, with g3, Bg2, d3, Be3, Nge2 and Qd2, or to the Grand Prix plan of f4, Nf3 and a queen transfer via e1 to h4; it can also transpose to open lines later. 2. c3, the Alapin, prepares d4 so that a capture is answered by cxd4, preserving a two-pawn center; Black typically replies 2...Nf6 or 2...d5. 2. d4 cxd4 3. c3 is the Smith-Morra Gambit, a pawn for development. 2. f4, the McDonnell Attack, allows 2...d5, and 2. Bc4, the Bowdler Attack, is defused by ...e6 and ...d5 and scores poorly for White online.

Polerio examined 1...c5 in a manuscript of 1594, and the name is thought to derive from the Sicilian-born Pietro Carrera. La Bourdonnais used it in his 1834 matches against McDonnell, but leading players turned against it in the late nineteenth and early twentieth centuries. It recovered in the 1940s and 1950s, and Fischer and Kasparov, who relied on it almost exclusively, established it as Black's most ambitious answer to 1. e4; Carlsen also plays it regularly. It is among the most frequently reached named positions, results are nearly even, and the engine assessment is close to balance.